Method for producing decorative glass objects

ABSTRACT

A method for producing decorative glass objects in which the decoration is created by blisters formed by air bubbles within solid glass and/or by a pattern on the outer surface of the glass. When producing glass objects provided with air bubbles by means of known methods the bubbles remain on the surface of the objects which then easily break. In addition, the bubbles are formed at random, which may make them appear as dim impurities. When, in accordance with the invention, molten glass is poured from above in the shape of a band into a hot mould, the molten glass is spread into the mould in layers between which microscopic air bubbles remain. As the glass surface cools, the air enclosed within the bubbles expands in the molten glass which, while cooling, leaves the bubbles as clear pearls inside the glass. As the molten glass is spread in layers towards the wall of the mould, a pattern is formed as the glass surface cools.

The present invention relates to a method for producing decorative glassobjects in which the decoration is created by clear pearls formed by airbubbles within solid glass and/or by a pattern essentially formed bystreaks on the outer surface of the glass.

Glass with bubbles has previously been produced either by using sodiumcarbonate or by boiling molten glass in a furnace before starting theproduction in order to produce blisters. However, when using thesemethods, the outcome has not been controllable but has been ratherrandom, which has resulted in an extremely high waste percentage.Moreover, these methods have only been applicable to manualglass-making.

The use of sodium carbonate has resulted in too big bubbles or too smallbubbles appearing as a dim impurity in the glass. Bubbles producedduring boiling as well as by using sodium carbonate remain on the outerand inner surfaces of the objects, which thus become fragile.

The accompanying drawing illustrates some applications of the invention.

FIG. 1 is a front view of a length cut off from a cylindrical, solidglass object.

FIG. 2 shows the same in cross-section. Inside the glass object thereare blisters or pearls 1 of different sizes and on the surface streaks 2to a small extent.

FIG. 3 illustrates a stem glass provided with a solid stem 3 made bymeans of the method according to the invention and having blisters 4inside and streaks 5 on the outer surface. To this stem 3 has beensecured by blowing a bowl 6 made simultaneously therewith.

FIG. 4 is a front view of a drinking glass provided with a solid stemportion 7 made by means of the method according to the invention andwith a bowl portion 8 produced simultaneously therewith and securedthereto by blowing. The stem portion is provided with blisters 9 andstreaks 10.

By means of the method according to the invention fully clear pearls canbe produced within the glass. The variable size of the pearls and their"arbitrary" grouping create a strong impression of beauty resembling theoverall impression given by the Archipelago Sea, for which reason themethod according to the invention is called the "Arkipelago" method.

By means of the method it is also possible to provide the outer surfaceof glass with a pattern mainly consisting of streaks. Both the patternand the blisters formed by pearls are fully controllable. Theproportions of both the pattern and the blisters can each be separatelyincreased or reduced, the extreme cases essentially comprising blistersonly or essentially pattern only (blisters always appear to someextent).

According to the invention, molten glass is poured in the shape of aband either mechanically or manually from above into a hot mould wherebythe glass is spread into the mould in layers between which microscopicair bubbles remain. The temperature of the mould is lower than thetemperature of the glass melt poured whereby, as the glass surfacecools, the core still remains hot and the air enclosed within thebubbles expands in the still molten glass which, while slowly cooling,leaves the bubbles as clear pearls inside the glass. As the molten glassis spread in layers towards the wall of the mould, a pattern (forexample, comprising streaks) is formed as the glass surface cools.

In connection with the invention, it has been found that, in order toproduce satisfactory blisters and a satisfactory pattern, the moltenglass must be poured in the shape of a band into the moulds from arelatively high level. A level of about 50 to 70 cm has proved to beadvantageous. Within this range, a wide control of both the blisters andthe pattern is possible. If a lower level is used, there will be lessblisters and less pattern and, when pouring the molten glass from alevel right above the mould, the effect according to the invention willno longer be obtained.

In addition to the pouring level, the blisters and the pattern can alsobe controlled by means of the quantity of molten glass poured. Thebigger the quantity of molten glass poured per unit of time is, thesmaller will be the effect obtained according to the invention. Saidquantity, of course, depends on the cross-sectional area of the mould.When molten glass is poured through a nozzle, the ratio between thecross-sectional area of the nozzle opening and the cross-sectional areaof the mould will determine the relative quantity of molten glass pouredper unit of time. As this ratio is increased, the quantity of moltenglass increases and the proportion of blisters and pattern is reduced.

The nozzle may be of any appropriate cross-sectional shape, for example,of a circular or elliptical shape.

As stated above, the formation of blisters and pattern can be controlledin the desired manner by means of the pouring level and the quantity ofmolten glass poured. The blisters and the pattern produced in glassobjects are fully controllable and reproducable. Due to this, the methodcan be carried into effect both manually and mechanically. It is alsopossible to produce a decorative glass object batchwise (chargewise), inwhich case the pouring level and/or the quantity of poured glass ischanged between batches. In this way, a fairly high glass object can beproduced, in which the decorative effect varies in the verticaldirection and corresponds to the conditions of the batches used.

The method according to the invention may be combined with traditionalglass-making methods. Thus, for example, the bowl portions of drinkingglasses and bowls can be secured by blowing to a stem portionsimultaneously made by means of the method according to the inventioneither by using blowing by blowpipe or automatic equipment.

What I claim is:
 1. A method for producing a decorative glass object inwhich the decoration is created by blisters formed by air bubbles withinsolid glass and/or by a pattern on the outer surface of the glass,characterized in that molten glass is poured from above in the shape ofa band into a hot mould at a suitable distance above said mould wherebysaid molten glass is spread in layers into said mould between which airbubbles remain to form said blisters, the temperature of the mould beinglower than the temperature of the molten glass, whereby as the glasssurface cools, the core still remains hot and air enclosed within thebubbles expands in the still molten glass which, while cooling, formsclear pearls inside the glass.
 2. A method as claimed in claim 1,characterized in that the desired blisters and/or the desired patternare produced by selecting an appropriate pouring level.
 3. A method asclaimed in claim 2, characterized in that the molten glass is pouredinto the mould from a height between 50 to 70 cm.
 4. A method as claimedin claim 1 or 2 or 3, characterized in that the desired extent ofblisters and/or the desired pattern are controlled by controlling thequantity of molten glass poured per unit of time.
 5. A method as claimedin claim 1 or 2 or 3 further including the step of forming a portion ofthe decorative glass object by blowing a glass object in a conventionalmanner.
 6. A method as claimed in claim 5, characterized in that adecorative stem portion is made to which a bowl portion of a drinkingglass or of a bowl is secured by blowing.